<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <title>Vue</title>
    <script src="https://unpkg.com/vue/dist/vue.js"></script>
</head>
<body>

<div id="app_d_x">
    <input type="radio" id="usa" value="USA" v-model="picked">
    <label for="usa">USA</label>
    <input type="radio" id="china" value="CHINA" v-model="picked">
    <label for="china">CHINA</label>
    <br/>
    选择的值：<p>{{picked}}</p>
</div>

<script>
    let v = new Vue({
        el: '#app_d_x',
        data: {
            picked: 'USA',
        }
    });
</script>

</body>
</html>